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1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * This file is part of the Linux kernel.
4  *
5  * Copyright (c) 2011-2014, Intel Corporation
6  * Authors: Fenghua Yu <fenghua.yu@intel.com>,
7  *          H. Peter Anvin <hpa@linux.intel.com>
8  */
9 
10 #ifndef ASM_X86_ARCHRANDOM_H
11 #define ASM_X86_ARCHRANDOM_H
12 
13 #include <asm/processor.h>
14 #include <asm/cpufeature.h>
15 
16 #define RDRAND_RETRY_LOOPS	10
17 
18 #define RDRAND_INT	".byte 0x0f,0xc7,0xf0"
19 #define RDSEED_INT	".byte 0x0f,0xc7,0xf8"
20 #ifdef CONFIG_X86_64
21 # define RDRAND_LONG	".byte 0x48,0x0f,0xc7,0xf0"
22 # define RDSEED_LONG	".byte 0x48,0x0f,0xc7,0xf8"
23 #else
24 # define RDRAND_LONG	RDRAND_INT
25 # define RDSEED_LONG	RDSEED_INT
26 #endif
27 
28 /* Unconditional execution of RDRAND and RDSEED */
29 
rdrand_long(unsigned long * v)30 static inline bool rdrand_long(unsigned long *v)
31 {
32 	bool ok;
33 	unsigned int retry = RDRAND_RETRY_LOOPS;
34 	do {
35 		asm volatile(RDRAND_LONG
36 			     CC_SET(c)
37 			     : CC_OUT(c) (ok), "=a" (*v));
38 		if (ok)
39 			return true;
40 	} while (--retry);
41 	return false;
42 }
43 
rdrand_int(unsigned int * v)44 static inline bool rdrand_int(unsigned int *v)
45 {
46 	bool ok;
47 	unsigned int retry = RDRAND_RETRY_LOOPS;
48 	do {
49 		asm volatile(RDRAND_INT
50 			     CC_SET(c)
51 			     : CC_OUT(c) (ok), "=a" (*v));
52 		if (ok)
53 			return true;
54 	} while (--retry);
55 	return false;
56 }
57 
rdseed_long(unsigned long * v)58 static inline bool rdseed_long(unsigned long *v)
59 {
60 	bool ok;
61 	asm volatile(RDSEED_LONG
62 		     CC_SET(c)
63 		     : CC_OUT(c) (ok), "=a" (*v));
64 	return ok;
65 }
66 
rdseed_int(unsigned int * v)67 static inline bool rdseed_int(unsigned int *v)
68 {
69 	bool ok;
70 	asm volatile(RDSEED_INT
71 		     CC_SET(c)
72 		     : CC_OUT(c) (ok), "=a" (*v));
73 	return ok;
74 }
75 
76 /*
77  * These are the generic interfaces; they must not be declared if the
78  * stubs in <linux/random.h> are to be invoked,
79  * i.e. CONFIG_ARCH_RANDOM is not defined.
80  */
81 #ifdef CONFIG_ARCH_RANDOM
82 
arch_get_random_long(unsigned long * v)83 static inline bool arch_get_random_long(unsigned long *v)
84 {
85 	return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_long(v) : false;
86 }
87 
arch_get_random_int(unsigned int * v)88 static inline bool arch_get_random_int(unsigned int *v)
89 {
90 	return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_int(v) : false;
91 }
92 
arch_get_random_seed_long(unsigned long * v)93 static inline bool arch_get_random_seed_long(unsigned long *v)
94 {
95 	return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_long(v) : false;
96 }
97 
arch_get_random_seed_int(unsigned int * v)98 static inline bool arch_get_random_seed_int(unsigned int *v)
99 {
100 	return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_int(v) : false;
101 }
102 
103 extern void x86_init_rdrand(struct cpuinfo_x86 *c);
104 
105 #else  /* !CONFIG_ARCH_RANDOM */
106 
x86_init_rdrand(struct cpuinfo_x86 * c)107 static inline void x86_init_rdrand(struct cpuinfo_x86 *c) { }
108 
109 #endif  /* !CONFIG_ARCH_RANDOM */
110 
111 #endif /* ASM_X86_ARCHRANDOM_H */
112